Because there are many possible solutions to a problem; it is important to choose the design requirements and success criteria for the proposed solution. Here the authors describe their design criteria for thoroughly mixing a solution.

Here the authors describe some possible applications that could benefit from this work. One specific application described is diffusion limited reactions which might happen at a surface such as those between an electrode and electrolytes in solution or between immobilized antibodies and antigens in solution. A previous annotation mentions a protein detection mechanism from blood samples which is dependent on a diffusion limited reaction.

The authors have proven that they have created a novel mixing technique which is more effective that standard diffusion mixing, easier to integrate into other microfluidic structurers than current mixing techniques, and doesn't require any complicated active device components.

A recent paper has been published (Protein detection in blood with single-molecule imaging) which demonstrates capturing of the target proteins within blood. This increases the effectiveness of their protein detection method.

Many health and biotechnology research and assays depend on the efficient sorting of cells. Microfluidics allows for efficient and accurate cell sorting due to the ability to interact with cells using physical structures and processes occurring on the same scale. This is useful in drug development, disease detection, and cellular research.

Chaotic flow allows for faster mixing as it allows for the fluid components to stretch and fold much sooner along the flow direction. This allows to achieve full mixing within a much smaller channel length.

Here the authors describe the exact steps that they use to create the devices. The techniques (photolithography) and materials (PDMS) described are commonly used in the fabrication of microfluidic devices.

Here the authors describe how they compared the mixing performance of 1) a straight microchannel, 2) a microchannel with straight ridges, and 3) a microchannel with staggered herringbone ridges to prove that their design (staggered herringbone ridges) had the best mixing performance.

"Here, the authors note that the ridge structures result in mixing not only in pressure driven flows but also in electroosmotic flows."

Here the authors describe the mathematical process of analyzing the data presented in Fig. 2B to determine the extent of the chaotic region.

Here the authors provide a description of the fluorescent streams used in the first 3 figures and how they were prepared.

When possible it is important to compare the data gathered experimentally with the expected result (determined logically or mathematically) to make sure that the experiments are valid and accurate within an acceptable range of error. Here the authors state that their experimental data qualitatively agrees with their mathematical model.

Aqueous buffer is a solution of weak acid and its conjugate base which provides a degree of stability to prevent the rapid fluctuation in pH when a small amount of strong acid or base is added.

Recently, this technology has been used to create a new method for the molecular profiling of circulating tumor cells (Covalent chemistry on nanostructured substrates enables noninvasive quantification of gene rearrangements in circulating tumor cells). This method would allow for noninvasive monitoring of disease progression and treatment guidance.

Learning Standard: Scientific Investigations Use a Variety of Methods (NS1). New technologies advance scientific knowledge. (HS-LS1-2). Without technologies such as photolithography or advanced microscopy the devices and methods utilized in this paper would not be possible.

Flows constrained along a single dimension such as those found in the microchannels of microfluidic devices.

Digital Object Identifier (DOI) is a standardized method for uniquely referencing digital documents with the aim of easily leading to the documents location. Almost all published academic journal articles as well as research reports and data sets have an assigned DOI.

To make uniform or similar.

Here the authors list where the funding for the research came from. A lot of academic research is funded through government grants (DARPA, NSF, NIH, Military, etc.).

Microfluidics offers the potential for rapid and efficient analysis of DNA and proteins at a lower cost then traditional analysis. This is perhaps one of the most widely used commercial applications of microfluidics and has recently been seen most prominently in SARS-CoV-2 and other immunology testing tasks.

Learning Standard: Constructing Evidence and Designing Solutions (SEP6). This standard states that there is a range of possible engineering solutions and the best is dependent upon the design requirements and the criteria used for evaluation. The authors list the design requirements of microfluidics as inexpensive, easy to operate, with few moving parts.

Learning Standard ETS1.C: Optimizing the Design Solution. The authors optimized the mixing design by changing the mixing elements to a staggered herringbone pattern.

Learning Standard ETS1.A: Defining and Delimiting an Engineering Problem. This standard requires students to accurately recognize and define an engineering problem. In this paper the authors are addressing a difficult problem, mixing fluids at the microscale.

Perpendicular to the direction of the flow along the channel

The measurement of a fluid's internal resistance to flow

At a right angle, perpendicular

Fluid flow that is subject to chaotic changes in velocity and pressure. The opposite of laminar flow.

Steady viscous (thick) fluid flow driven by an effective pressure gradient established between the two ends of a long straight pipe of uniform circular cross-section

Startup Outset Medical (https://www.outsetmedical.com/) has created a portable dialysis machine which utilizes the microfluidic technology discussed in this paper.

Chemical analysis technique involving the separation of components in a mixture by passing it through a material in which the components move at different rates.

[Chromatography basics video] https://www.youtube.com/watch?v=XfSopnqrHOs)